package com.xm9m.web.service.utils.weichat;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Arrays;

/**
 * Created by Liutong on 2016/7/19.
 */

public class SignUtil {

    // 与接口配置信息中的Token要一致
    private static String token = "xm9m2016";

    /**
     * 验证签名
     *
     * @param signature 微信加密签名
     * @param timestamp 时间戳
     * @param nonce     随机数
     * @return
     */
    public static boolean checkSignature(String signature, String timestamp,
                                         String nonce) {

        String[] arr = new String[]{
                token, timestamp, nonce
        };
// 将token、timestamp、nonce三个参数进行字典序排序
        Arrays.sort(arr);
        StringBuilder content = new StringBuilder();
        for (int i = 0; i < arr.length; i++) {

            content.append(arr[i]);

        }
        MessageDigest md = null;
        String tmpStr = null;

        try {

            md = MessageDigest.getInstance("SHA-1");
// 将三个参数字符串拼接成一个字符串进行sha1加密
            byte[] digest = md.digest(content.toString().getBytes());
//字节转字符串
            tmpStr = byteToStr(digest);

        } catch (NoSuchAlgorithmException e) {

            e.printStackTrace();

        }

        content = null;
// 将sha1加密后的字符串可与signature对比，标识该请求来源于微信
        return tmpStr != null ? tmpStr.equals(signature.toUpperCase()) : false;

    }

    /**
     * 将字节数组转换为十六进制字符串
     *
     * @param byteArray
     * @return
     */
    private static String byteToStr(byte[] byteArray) {

        String strDigest = "";
        for (int i = 0; i < byteArray.length; i++) {

            strDigest += byteToHexStr(byteArray[i]);

        }
        return strDigest;

    }

    /**
     * 将字节转换为十六进制字符串
     *
     * @param mByte
     * @return
     */
    private static String byteToHexStr(byte mByte) {

        char[] Digit = {
                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A',
                'B', 'C', 'D', 'E', 'F'
        };
        char[] tempArr = new char[2];
        tempArr[0] = Digit[(mByte >>> 4) & 0X0F];
        tempArr[1] = Digit[mByte & 0X0F];

        String s = new String(tempArr);
        return s;

    }

}
